With a popularization of mobile terminals such as smart phones, a user may use a mobile phone more frequently. Thus, a demand for battery capacity in the mobile phone increases. However, since the battery capacity in the mobile phone is limited by a space inside of the mobile phone, it is difficult to provide a satisfied endurance of the battery to the user. Therefore, a mobile phone with double-batteries has sprung up.
In general, when charging the mobile phone with double-batteries, after one of two batteries is full, the other one may start charging. A charging efficiency under this circumstance is relatively low.